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Diabetes: Protecting Your Vision

Diabetes is a disease that affects the body’s ability to produce or use insulin effectively to control blood sugar (glucose) levels. Although glucose is an important source of energy for the body’s cells, too much glucose in the blood for a long time can cause damage in many parts of the body, including the heart, kidneys, blood vessels and the small blood vessels in the eyes.

Diabetes can cause vision in both eyes to change, even if you do not have retinopathy (damage to the retina). Rapid changes in your blood sugar alter the shape of your eye's lens, and the image on the retina will become out of focus. After your blood sugar stabilizes, the image will be back in focus. You can reduce episodes of blurred vision by maintaining good control of your blood sugar.

There are three types of diabetes. Type 1 diabetes is usually diagnosed in children and young adults. Previously known as juvenile diabetes, it occurs when the body does not produce insulin. The most common form of diabetes is type 2 diabetes. In this case, either the body does not produce enough insulin or the body's cells ignore the insulin. In gestational diabetes, blood sugar levels become elevated during pregnancy in women who have never had diabetes before. Gestational diabetes starts when the mother's body is not able to make and use all the insulin it needs during pregnancy.

People with any type of diabetes can develop hyperglycemia, which is an excess of blood sugar, or serum glucose. A chronic elevation of serum glucose causes damage throughout the body, including the small blood vessels in the eyes.

When the blood vessels in the retina (the light sensitive tissue lining the back of the eye) swell, leak or close off completely – or if abnormal new blood vessels grow on the surface of the retina – it is called diabetic retinopathy.

Diabetic retinopathy usually affects both eyes. People who have diabetic retinopathy often don't notice changes in their vision in the disease's early stages. But as it progresses, diabetic retinopathy usually causes vision loss that in many cases cannot be reversed. The changes may be slightly different, depending on which type of diabetic retinopathy is the cause.

When blood sugar levels are too high for extended periods of time, it can damage capillaries (tiny blood vessels) that supply blood to the retina. Over time, these blood vessels begin to leak fluids and fats, causing edema (swelling). Eventually, these vessels can close off, called ischemia. These problems are signs of non-proliferative diabetic retinopathy (NPDR).

NPDR is the earliest stage of diabetic retinopathy. With this condition, damaged blood vessels in the retina begin to leak extra fluid and small amounts of blood into the eye. Sometimes, deposits of cholesterol or other fats from the blood may leak into the retina. NPDR can cause small bulges in ocular blood vessels, retinal hemorrhages, swelling of the eye and the closing of small ocular blood vessels. All these changes can affect vision.

As diabetic eye problems are left untreated, proliferative diabetic retinopathy (PDR) can develop. Blocked blood vessels from ischemia can lead to the growth of new abnormal blood vessels on the retina (called neovascularization), which can damage the retina by causing wrinkling or retinal detachment. Neovascularization can even lead to glaucoma, damage to the optic nerve that carries images from your eye to your brain.

Several factors can influence the development and severity of diabetic retinopathy. One of the most basic is blood sugar levels. But it’s also the easiest factor to affect. Lower blood sugar levels can delay the onset and slow the progression of diabetic retinopathy, so it’s important to control your blood sugar.

Another factor in diabetic retinopathy is blood pressure. A major clinical trial demonstrated that effectively controlling blood pressure reduces the risk of retinopathy progression and visual acuity deterioration. High blood pressure damages your blood vessels, raising the chances for eye problems. Target blood pressure for most people with diabetes is less than 130/80 mmHg.

The risk of developing diabetic retinopathy or having your disease progress increases over time. After 15 years, 80 % of type 1 patients will have diabetic retinopathy. After 19 years, up to 84% of patients with type 2 diabetes will have diabetic retinopathy.

Ethnicity is also a factor. While diabetic retinopathy can happen to anyone with diabetes, certain ethnic groups are at higher risk because they are more likely to have diabetes. These include African Americans, Latinos and Native Americans.

Maintaining strict control of blood sugar and blood pressure, as well as having regular diabetic retinopathy screenings by your ophthalmologist (MD), are keys to preventing diabetic retinopathy and vision loss. If you have diabetes, you should see your ophthalmologist for a yearly diabetic retinopathy screening with a dilated eye exam; even if your vision seems fine, it's important to detect diabetic retinopathy in the early stages. If you become pregnant, your eye doctor may recommend additional eye exams throughout your pregnancy, because pregnancy can sometimes worsen diabetic retinopathy.